Initial degree of impregnation of out-of-autoclave prepreg

Student: Marc Palardy-Sim

Supervisor: Prof. Pascal Hubert

Sponsors: NSERC, Bombardier

Out-of-autoclave (OOA) prepregs have shown potential to produce high quality parts with reduced capital and operating costs compared to traditional autoclave techniques. However, due to the reduction in consolidation pressure, there is still difficulty manufacturing large and complex parts. Previous research has studied the effects of various processing parameters on final part quality. This study focuses on quantifying the initial prepreg state in order to link this with final part quality. The particular parameter of interest is the resin degree of impregnation – effectively a measure of how many fibres are surrounded by resin. OOA prepregs are manufactured with dry fibre regions to allow for gas removal during resin cure. If the degree of impregnation is too low, there will not be enough time to remove all the entrapped air before the resin gels. If the degree of impregnation is too high, the evacuation channels will be restricted and it may not be possible to remove all the gases released during the polymerization reaction.

Schematic of prepreg impregnation schemes for unidirectional as well as a tow from a woven architecture

Currently existing techniques used to measure prepreg degree of impregnation are either destructive, have low repeatability, require many hours of processing, or do not measure local problems. One of these techniques, micro computed tomography, can be used to qualitatively and quantitatively visualize dry two regions. Using a novel technique, the degree of impregnation of unprocessed prepreg specimens is measured and compared to traditional techniques. Not only does this technique show promise for quickness and accuracy of measurement, it also has the possibility for in-line integration.

Micro-CT image used to measure tow degree of impregnation